The invention concerns cam gears for textile machines, especially for pattern controlling of warp-knitting machines provided with cams having rest and transition areas.
Known embodiments of cam gears, for instance for controlling displacement of guide bars of a warp-knitting machine, consist of a cam, a cam-follower and transfer elements for the guide bar. The cam profile consists of various alternately arranged rest and transistion areas, wherein the rest areas theoretically represent stops for the cam follower, and the transition areas are provided with shapes for achieving a jerk-free and jolt-free movement for the cam follower, whereof the general functioning is known in the technical literature (VDI-Richtlinie No. 2143, table 1, page 5, anthology (Editor J. Volmer): Getriebetechnik-Lehrbuch, 4. edition 1980, page 359).
These cam profiles are evaluated and selected according to kinematic values. For the motion of the transfer element, a curve is determined which lies between the two adjacent rest areas, the extreme values of which are located at the transition points of the rest areas i.e. no further maximum or minimum points are permitted between the two rest areas. It is important that the transition points are located on the first lead-in derivation.
Because of the finite rigidity of the transfer elements of the cam gear in conjunction with the working mechanism, they form an oscillating system of which the lowest oscillating frequency cannot be increased freely.
For this reason, in conventional cam gears, the transfer elements receive at the rest area oscillations which frequently result in the periodically repeating unstable transition conditions. Because of the occurring oscillations, the rest is not theoretically attained, and the working mechanism does not remain in the required resting position and executes undesired additional movements. Along with the resonance phenomena errors occur in the rest area which can cause, for instance, interferences in the stitch formation process in fast running warp-knitting machines.
In similar fashion, oscillations occurring in cam gears of textile machines cause transition movements between rest areas. The attainable normal speed is thereby often limited, i.e. malfunctions occur.